This invention is generally directed to a brake lamp illumination system for a trailer. More particularly, the invention contemplates a brake lamp illumination system for a trailer which is activated by sensing the speed of wheel rotation or deceleration of a wheel.
A standard tractor-trailer includes a tractor and a trailer. A seven-way connector provides the electrical connection between the tractor and the trailer. The seven-way connector includes a wiring harness which has seven circuits therein, which, as known in the art, are coded as the brown circuit, the green circuit, the red circuit, the white (ground) circuit, the black circuit, the yellow circuit and the blue (auxiliary) circuit.
A standard tractor-trailer uses two braking systems, a primary service brake and a secondary emergency/parking brake. The primary service brake is a fully pneumatic system, using air pressure for signaling the application of the brakes. Federally required brake lamps are used to indicate primary service brake application. The brake lamps are controlled by a pneumatic pressure switch mounted on the tractor and connected to the service brake control line. Thus, when the service brake is applied, the pneumatic pressure switch closes, completing the electrical circuit to the brake lamps mounted on the tractor. The electrical connection to the brake lamps is provided by the red circuit of the seven-way connector to the brake lamps on the trailer.
The secondary emergency/parking brake uses the loss of air to signal the application of the springs to apply the brakes. Thus, if air pressure in the braking system is lost, the emergency brake will automatically cause large springs on the brakes to apply the brakes to stop the tractor-trailer. Because the brake pedal has not been applied in this situation, the pneumatic pressure switch has not closed to signal power to be supplied to the brake lamps through the red circuit. Therefore, when the secondary braking system is used to slow the vehicle, the brake lamps are not illuminated.
The problem with this braking system is that upon an emergency brake activation, the driver of the vehicle following the trailer does not have warning that the trailer is rapidly coming to a stop. It is obvious what can happen when a trailer stops rapidly without warning to the driver behind it. Additionally, no warning is given to the driver behind the trailer when the trailer is slowing down for a reason other than application of the service brakes.
Anti-lock braking systems (ABS) are currently used in most trailers. Anti-lock braking systems aid the braking system of a vehicle by preventing the wheels of a vehicle from locking up during braking. Locking-up of the wheel reduces the effectiveness of the braking and allows less control of the vehicle. If the rotation of the wheel suddenly changes, then the ABS senses that the wheel has locked-up. Once the ABS senses brake lock-up, a central processing unit (CPU) signals the service valve to momentarily release the brakes to allow the wheel to rotate again and then signals to reapply the brakes. Thus, the ABS allows for greater control of the vehicle during braking.
The blue (auxiliary) circuit of the seven way connector is used to power the ABS. Since approximately 1997 in North America, new tractors have been built so that the blue circuit provides full time power for the ABS. For tractors built prior to that time, the blue circuit was switchable. Thus, when a tractor built prior to 1997 is in operation, power may or may not be supplied to the ABS through the blue circuit. Because it is possible that a new trailer with ABS will be pulled by an older tractor which does not provide full time power to the ABS through the blue circuit, the red circuit is electrically connected to the ABS as an alternate means of powering the ABS when power is not provided through the blue circuit. Because it is only necessary to power the ABS when the brakes are applied, providing power to the ABS through the red circuit is sufficient. Thus, when the brakes are applied power will be provided to the ABS and to the brake lamps through the red circuit.
Changes in federal law now require full time power to the ABS during operation. The present invention, which is described in detail below, is operable only with new tractors which have full time power to the blue circuit for the ABS.
The present invention provides a brake lamp illumination system which overcomes the problems presented in the prior art and which provides additional advantages over the prior art, such advantages will become clear upon a reading of the attached specification in combination with a study of the drawings.
A general object of the present invention is to provide a brake lamp illumination system for a trailer in which the brake lamps will illuminate without use of the brake pedal.
An object of the present invention is to provide a brake lamp illumination system for a trailer in which the brake lamps will illuminate when the emergency brake is applied.
Another object of the present invention is to provide a brake lamp illumination system for a trailer in which the brake lamps will illuminate when the vehicle decelerates.
A specific object of the present invention is to provide a brake lamp illumination system in which the brake lamps of the trailer are illuminated when a wheel speed sensor senses deceleration of the wheel of the vehicle.
A specific object of the present invention is to provide a brake lamp illumination system in which the brake lamps of the trailer are illuminated when an accelerometer senses deceleration of the wheels of the trailer.
Briefly, and in accordance with the foregoing, the present invention discloses a brake lamp illumination system for a trailer in which the brake lamps of the trailer are illuminated not only when the brake pedal is applied, but also when the speed of the trailer is decreasing.